Polyurethane coating material composition, multistage coating methods using these coating material compositions, and also the use of the coating material composition as clearcoat material and pigmented coating material, and application of the coating method for automotive refinish and/or for the coating of plastics substrates and/or of utility vehicles

ABSTRACT

The present invention relates to coating material compositions comprising at least one polyhydroxyl group-containing compound (A), at least one polyisocyanate group-containing compound (B) having free and/or blocked isocyanate groups, and at least one catalyst (D) based on a zinc-amidine complex which is prepared by reaction of 1.0 moles of at least one zinc(II) biscarboxylate with less than 2.0 moles of at least one amidine 
     
       
         
         
             
             
         
       
     
     where R 5 =hydrogen and R 1 , R 2 , R 3 , and R 4  are each identical or different radicals, R 1  and R 3  being hydrogen or an alkyl radical or an aryl radical, and R 2  and R 4  being an alkyl radical or an aryl radical.

The present invention relates to coating material compositionscomprising at least one polyhydroxyl group-containing compound (A), atleast one polyisocyanate group-containing compound (B), and at least onecatalyst (D) based on a zinc-amidine complex.

The present invention additionally provides multistage coating methodsusing these coating material compositions, and also the use of thecoating material compositions as clearcoat material, and application ofthe coating method for automotive refinish and/or for the coating ofplastics substrates and/or of utility vehicles.

Polyurethane coating materials typically comprise a catalyst, and inthis context not only acidic compounds but also, in particular, tertiaryamines and/or metallic compounds, such as various tin compounds, forexample, more particularly dibutyltin dilaurate and dibutyltin oxide,are employed.

The employment of tin-containing catalysts is to be avoided in coatingmaterials, as elsewhere, because of the toxicity inherent in many tincompounds. The EU Commission's Working Group on Classification andLabelling” have categorized dibutyltin oxide (DBTO) and dibutyltindilaurate (DBTL) accordingly.

The article available on the Internet at the address www.wernerblank.comand titled “Catalysis of the Isocyanate-Hydroxyl Reaction by Non-TinCatalysts”, by Werner J. Blank, Z. A. He, and Ed. T. Hessell of thecompany King Industries Inc., therefore describes alternatives to thetypical tin-containing catalysts based on various metal salts and metalcomplexes, such as zirconium chelates, aluminum chelate, and bismuthcarboxylate.

DE 10 2008 061 329 A1 discloses coating materials where the use ofmetal-containing catalysts is to be avoided as far as possible and whichinstead as catalyst comprise 1,3 substituted imidazolium salts for thedeblocking of blocked polyisocyanates in polyurethane coating materials.

WO04/029121 describes polyurethane compositions which are stabilized interms of the reactivity of the composition by addition of acids with apKa range between 2.8 and 4.5, these acids being able to be utilized atthe same time as catalyst. Acids used in this context and with a pKarange between 2.8 and 4.5 include, for example, benzoic acid,hydroxybenzoic acid, salicylic acid, phthalic acid, and so on. Thecompositions preferably comprise no further catalyst, although inaddition it is also possible to use the typical known polyurethanecatalysts, such as tertiary amines or amidines or organometalliccompounds, such as tin compounds more particularly. Where amines areused as catalyst, it is necessary to employ great care in the selectionof the type of amine and its amount, since the aminic catalysts are ablein part to eliminate the stabilizing action of the organic acids added.

U.S. Pat. No. 5,847,044 describes polyurethane powder coating materialswhich as catalysts comprise N,N,N′-trisubstituted amidines, moreparticularly bicyclic amidines.

WO 09/135600 describes polyurethane compositions, more particularlysealants, adhesives, and foams, which comprise as catalyst the reactionproduct of a metal salt with nitrogen-containing, heterocycliccompounds, more particularly substituted imidazoles.

DE-A-24 34 185 describes a process for preparing amidine-metal complexesand their use as catalysts for the isocyanate polyaddition reaction.These amidine-metal complexes are prepared by reacting an amidine with a0.5- to 4-fold molar amount of a metal compound, the amidines usedcomprising not only monocyclic and/or bicyclic compounds, such asimidazoles more particularly, but also acyclic compounds, such asformamidines, acetamidines, benzamidines, and guanidines. Metalcompounds used are those of trivalent iron, of divalent nickel, ofdivalent zinc, of divalent manganese, of divalent tin or of tetravalenttin, with the corresponding carboxylates being employed moreparticularly.

Lastly, U.S. Pat. No. 7,485,729 B2 and also the equivalentspecifications WO06/022899, US 2006/0247341 A1, and US 2009/0011124 A1,describe organometallic compounds and coating materials comprising them.Coating materials described are powder coating materials based onhydroxyl-containing polyacrylates and/or polyesters and onuretdione-containing polyisocyanates, liquid coating materials based onhydroxyl-containing polyacrylates and/or polyesters and on blockedpolyisocyanates, and also solventborne coating materials based onepoxy/carboxy or epoxy/anhydride components. The organometalliccompounds used as catalyst, besides other metal-amidine complexes, arecyclic or acyclic zinc biscarboxylate-bisamidine complexes, such asZn(1,1,3,3-tetramethylguanidine)₂(2-ethylhexanoate)₂, for example.

Problem

A problem addressed by the present invention, therefore, was that ofproviding coating material compositions, more particularly forautomotive refinish and for the coating of utility vehicles, that ensuregood assembly strength after just a very short time, meaning that theyought to ensure rapid curing even under the conditions of refinish andof the finishing of utility vehicles, in other words ought after curingat 60° C. for 30 minutes already to have undergone curing to an extentsuch that initial assembly operations or demasking operations can becarried out without damage to the coating. At the same time, however,the coating material compositions ought, at room temperature and aftermixing of the binder component with the isocyanate component, to have agood potlife of at least 2 hours. Potlife here means the period of timewithin which the coating material composition has attained twice itsinitial viscosity. Moreover, the coating material compositions ought tolead to coatings exhibiting good through-curing and sufficient ultimatehardness. Furthermore, these coating material compositions ought not toshow any changes in color before and after curing. Particularly in thefield of clearcoat materials in the automotive industry, the intrinsiccolor of the systems is subject to cracking requirements. Thus thecatalyst neither must exhibit any intrinsic color and nor must it leadto discoloring at mixing or during curing of the coating material whenthe catalyst is mixed with the typical components of a coating material.The resultant cured coatings ought, furthermore, to have no tendencytoward yellowing after exposure in the test known as the WOM test(WOM=Weather-Ometer Test, determined in accordance with SAE (Society ofAutomotive Engineers) Standard J2527_(—)04). Yellowing is determinedusing the multiple angle colorimeter BYK-mac from BYK-Gardner GmbH,D-82538 Geretsried, with calculation according to DIN 6174.

Furthermore, the catalyst ought to be able to be added to the coatingsystem from the outset. However, admixing the catalyst to the coatingsystems from the outset is not to cause any adverse effect on theshelflife of the coating composition. Furthermore, the catalyst ought tobe insensitive to hydrolysis, since even in systems in organic solution,the typically high concentration of hydroxyl groups can result in areduction in catalyst activity over the storage period. Especially inthe automotive refinish segment, an extremely long shelflife even atrelatively high temperatures is an advantage.

Lastly, the coating material compositions ought to be able to beprepared simply and with very good reproducibility, and ought not tocause any environmental problems during application. More particularly,catalysts containing tin ought to be avoided or at best be entirelydispensible.

Solution to the Problem

In the light of the addressed problem set out above, a coating materialcomposition has been found comprising at least one polyhydroxylgroup-containing compound (A), at least one polyisocyanategroup-containing compound (B) having free and/or blocked isocyanategroups, and

at least one catalyst (D) based on a zinc-amidine complex which ispreparable by reaction of 1.0 moles of one or more zinc(II)biscarboxylates with less than 2.0 moles of an amidine of the formula(I) or with less than 2.0 moles of a mixture of two or more amidines ofthe formula (I)

where R₅=hydrogen and R₁, R₂, R₃, and R₄ are each identical or differentradicals, R₁ and R₃ being hydrogen or an alkyl radical or an arylradical, and R₂ and R₄ being an alkyl radical or an aryl radical.

The present invention additionally provides multistage coating methodsusing these coating material compositions, and also the use of thecoating material compositions as clearcoat material, and application ofthe coating method for automotive refinish and/or for the coating ofplastics substrates and/or of utility vehicles.

It is surprising and was not foreseeable that the coating materialcompositions ensure good assembly strength after just a very short timeunder the conditions for automotive refinish, in other words they ensurerapid curing even under the conditions of refinish, thus being alreadytack-free after curing at 60° C. for 30 minutes. At the same time, atroom temperature and after mixing of the binder component with theisocyanate component, however, the coating material compositions exhibita good potlife of at least 2 hours. By potlife here is meant the periodof time within which the coating material composition has attained twiceits initial viscosity.

Moreover, the coating material compositions lead to coatings having goodthrough-curing and a sufficient ultimate hardness. Furthermore, thecatalyst neither exhibits an inherent color nor does it lead to adiscoloration with the conventional coating components while mixing orcuring the coating material. Moreover, the resultant cured coatings donot tend toward yellowing following exposure in the WOM test(WOM=Weather-Ometer Test, determined in accordance with SAE (Society ofAutomotive Engineers) Standard J2527_(—)04).

Furthermore, the catalyst can be added to the coating system from theoutset without adversely affecting the shelflife of the coating materialcompositions. Furthermore, the catalyst is insensitive to hydrolysis,and so the typically high concentration of hydroxyl groups does notresult in any reduction in the catalyst activity over the storageperiod, even in systems in organic solution, and this is an advantageespecially in the automotive refinish segment.

Lastly, the coating material compositions can be prepared easily andwith very good reproducibility, and do not cause any environmentalproblems during application. In particular, tin catalysts can be avoidedand at best are in fact entirely dispensible.

the Polyhydroxyl Group-Containing Compound (A)

As polyhydroxyl group-containing compound (A) it is possible to use allcompounds known to the skilled person which have at least 2 hydroxylgroups per molecule and are oligomeric and/or polymeric. As component(A) it is also possible to use mixtures of different oligomeric and/orpolymeric polyols.

The preferred oligomeric and/or polymeric polyols (A) have mass-averagemolecular weights Mw >500 daltons, measured by means of gel permeationchromatography (GPC) against a polystyrene standard, preferably between800 and 100 000 daltons, more particularly between 1000 and 50 000daltons.

Particularly preferred are polyester polyols, polyurethane polyols,polysiloxane polyols, polyacrylate polyols and/or polymethacrylatepolyols, and also copolymers thereof, referred to below as polyacrylatepolyols.

The polyols preferably have an OH number of 30 to 400 mg KOH/g, moreparticularly between 100 and 300 KOH/g. The hydroxyl number (OH number)indicates the number of mg of potassium hydroxide that are equivalent tothe amount of acetic acid bound by 1 g of substance on acetylation. Forthe determination, the sample is boiled with acetic anhydride-pyridineand the resultant acid is titrated with potassium hydroxide solution(DIN 53240-2). In the case of pure poly(meth)acrylates, the OH numbermay also be determined with sufficient accuracy by calculation on thebasis of the OH-functional monomers used.

The glass transition temperatures, measured by means of DSC measurementin accordance with DIN EN ISO 11357-2, of the polyols are preferablybetween −150 and 100° C., more preferably between −120° C. and 80° C.

Suitable polyester polyols are described in EP-A-0 994 117 and EP-A-1273 640, for example. Polyurethane polyols are prepared preferably byreaction of polyester polyol prepolymers with suitable di- orpolyisocyanates, and are described in EP-A-1 273 640, for example.Suitable polysiloxane polyols are described in WO-A-01/09260, forexample, and the polysiloxane polyols recited therein may be employedpreferably in combination with other polyols, more particularly thosehaving higher glass transition temperatures.

With very particular preference, component (A) comprises one or morepolyacrylate polyols and/or polymethacrylate polyols. Together with thepolyacrylate polyol(s) and/or polymethacrylate polyol(s) it is possiblefor other oligomeric and/or polymeric polyhydroxyl group-containingcompounds to be employed, examples being polyester polyols, polyurethanepolyols, and polysiloxane polyols, especially polyester polyols.

The poly(meth)acrylate polyols that are especially preferred inaccordance with the invention are generally copolymers and preferablyhave mass-average molecular weights Mw of between 1000 and 20 000daltons, more particularly between 1500 and 10 000 daltons, in each casemeasured by means of gel permeation chromatography (GPC) against apolystyrene standard.

The glass transition temperature of the copolymers is generally between−100 and 100° C., more particularly between −50 and 80° C. (measured bymeans of DSC measurements in accordance with DIN-EN-ISO 11357-2).

The poly(meth)acrylate polyols preferably have an OH number of 60 to 250mg KOH/g, more particularly between 70 and 200 KOH/g, and also an acidnumber of between 0 and 30 mg KOH/g.

The hydroxyl number (OH number) is determined as described above (DIN53240-2). The acid number here indicates the number of mg of potassiumhydroxide consumed for the neutralization of 1 g of the compound inquestion (DIN EN ISO 2114).

As hydroxyl-containing monomer building blocks it is preferred to usehydroxyalkyl acrylates and/or hydroxyalkyl methacrylates, such as moreparticularly 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropylacrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate,3-hydroxybutyl methacrylate, and, in particular, 4-hydroxybutyl acrylateand/or 4-hydroxybutyl methacrylate.

As further monomer building blocks for the poly(meth)acrylate polyols itis preferred to use alkyl acrylates and/or alkyl methacrylates, such aspreferably ethyl acrylate, ethyl methacrylate, propyl acrylate, propylmethacrylate, isopropyl acrylate, isopropyl methacrylate, butylacrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate,tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate, amylmethacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate,ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate,3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearylmethacrylate, lauryl acrylate or lauryl methacrylate, cycloalkylacrylates and/or cycloalkyl methacrylates, such as cyclopentyl acrylate,cyclopentyl methacrylate, isobornyl acrylate, isobornyl methacrylate or,in particular, cyclohexyl acrylate and/or cyclohexyl methacrylate.

As further monomer building blocks for the poly(meth)acrylate polyols itis possible to use vinylaromatic hydrocarbons, such as vinyltoluene,alpha-methylstyrene or, in particular, styrene, amides or nitriles ofacrylic or methacrylic acid, vinyl esters or vinyl ethers, and also, inminor amounts, in particular, acrylic and/or methacrylic acid.

the Polyisocyanate Group-Containing Compounds (B)

Suitable as component (B) are substituted or unsubstituted aromatic,aliphatic, cycloaliphatic and/or heterocyclic polyisocyanates that areknown per se. Examples of preferred polyisocyanates are as follows:2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane4,4′-diisocyanate, diphenylmethane 2,4′-diisocyanate, p-phenylenediisocyanate, biphenyl diisocyanates, 3,3′-dimethyl-4,4′-diphenylenediisocyanate, tetramethylene 1,4-diisocyanate, hexamethylene1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, isophoronediisocyanate, ethylene diisocyanate, 1,12-dodecane diisocyanate,cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane1,4-diisocyanate, methylcyclohexyl diisocyanates, hexahydrotoluene2,4-diisocyanate, hexahydrotoluene 2,6-diisocyanate, hexahydrophenylene1,3-diisocyanate, hexahydrophenylene 1,4-diisocyanate,perhydrodiphenylmethane 2,4′-diisocyanate, 4,4′-methylenedicyclohexyldiisocyanate (e.g. Desmodur® W from Bayer AG), tetramethylxylyldiisocyanates (e.g., TMXDI® from American Cyanamid), and mixtures of theaforementioned polyisocyanates. Preferred polyisocyanates are also thebiuret dimers and the isocyanurate trimers of the aforementioneddiisocyanates. Particularly preferred polyisocyanates (B) arehexamethylene 1,6-diisocyanate, isophorone diisocyanate, and4,4′-methylenedicyclohexyl diisocyanate, their biuret dimers and/ortheir isocyanurate trimers and/or their asymmetrical trimers, such as,for example, the asymmetrical HDI trimer available commercially underthe name Desmodur® N3900.

In another embodiment of the invention, the polyisocyanates arepolyisocyanate prepolymers having urethane structural units, which areobtained by reaction of polyols with a stoichiometric excess ofaforementioned polyisocyanates. Polyisocyanate prepolymers of this kindare described in U.S. Pat. No. 4,598,131, for example.

The polyisocyanate group-containing component (B) may be present in asuitable solvent (L). Suitable solvents (L) are those which allow asufficient solubility of the polyisocyanate component and are free fromisocyanate-reactive groups. Examples of such solvents are acetone,methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, methylisoamyl ketone, diisobutyl ketone, ethyl acetate, n-butyl acetate,ethylene glycol diacetate, butyrolactone, diethyl carbonate, propylenecarbonate, ethylene carbonate, N,N-dimethylformamide,N,N-dimethylacetamide, N-methyl-pyrrolidone, N-ethylpyrrolidone,methylal, butylal, 1,3-dioxolane, glycerol formal, benzene, toluene,xylene, n-hexane, cyclohexane, Solventnaphtha®, 2-methoxypropyl acetate(MPA), and ethyl ethoxypropionate.

Hydroxyl-Containing Compounds (C)

Optionally, in addition to the polyhydroxyl group-containing component(A), the coating material compositions of the invention may furthercomprise one or more monomeric, hydroxyl-containing compounds (C),different from component (A). These compounds (C) preferably occupy afraction of 0% to 20% by weight, more preferably of 1% to 10% by weight,very preferably of 1% to 5% by weight, based in each case on the bindercontent of the coating material composition.

As hydroxyl group-containing compound (C), use is made of low molecularmass polyols.

Low molecular mass polyols used are, for example, diols, such aspreferably ethylene glycol, neopentyl glycol, 1,2-propanediol,2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol,1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol,1,4-cyclohexanedimethanol and 1,2-cyclohexanedimethanol, and alsopolyols, such as preferably trimethylolethane, trimethylolpropane,trimethylolhexane, 1,2,4-butanetriol, pentaerythritol, anddipentaerythritol. Preference is given to admixing low molecular masspolyols of this kind in minor fractions to the polyol component (A).

Catalyst (D)

It is essential to the invention that the coating material compositioncomprises at least one catalyst (D) based on a zinc-amidine complexwhich is preparable by reaction of 1.0 moles of one or more zinc(II)biscarboxylates with less than 2.0 moles of an amidine of the formula(I) or with less than 2.0 moles of a mixture of two or more amidines ofthe formula (I)

where R₅=hydrogen and R₁, R₂, R₃, and R₄ are each identical or differentradicals, R₁ and R₃ being hydrogen or an alkyl radical or an arylradical, and R₂ and R₄ being an alkyl radical or an aryl radical.

The zinc-amidine complex is preferably either preparable by reaction of1.0 moles of one or more zinc(II) biscarboxylates with 0.1 to 1.8 moles,more preferably with 0.1 to 1.5 moles, and very preferably with 0.5 to1.0 moles, of an amidine of the formula (I), or preparable by reactionof 1.0 moles of one or more zinc(II) biscarboxylates with 0.1 to 1.8moles, more preferably with 0.1 to 1.5 moles, very preferably with 0.5to 1.0 moles, of a mixture of two or more amidines of the formula (I).

With particular preference the catalyst (D) is preparable by reaction of1.0 moles of the zinc(II) biscarboxylate with 0.1 to 1.8 moles, morepreferably with 0.1 to 1.5 moles, and very preferably with 0.5 to 1.0moles of an amidine of the formula (I).

The radicals R₂ and R₄ are preferably identical or different acyclic,straight-chain or branched alkyl radicals and/or identical or differentaryl radicals. Preferably, the radicals R₁ and R₃ are hydrogen oridentical or different acyclic, straight-chain or branched alkylradicals and/or identical or different aryl radicals. The alkyl radicalsmay in each case optionally be present as esters, ethers, ether esters,and ketones. The aryl radicals may be substituted by aliphatic esters,ethers, ether esters, and ketones, or be present as aromatic esters,ethers, ether esters, and ketones.

More preferably, the radicals R₁, R₂, R₃, and R₄ are each identical ordifferent acyclic aliphatic radicals, and very preferably these radicalsR₁, R₂, R₃, and R₄ have one to four carbon atoms. With particularpreference the radicals R₁, R₂, R₃, and R₄ are methyl radicals.

Preferred zinc-amidine complexes (D) are additionally those in which thecarboxylate radical of the zinc-amidine complex (D) is selected from thegroup of the carboxylate radicals of aliphatic linear and/or branched,optionally substituted monocarboxylic acids having 1 to 12 C atoms inthe alkyl radical and/or of aromatic, optionally substitutedmonocarboxylic acids having 6 to 12 C atoms in the aryl radical. Thecarboxylate radical largely determines the solubility of the resultantcomplex in the coating components used. With very particular preference,therefore, the complexes used in the coating material compositions ofthe invention are zinc-amidine complexes which are obtainable byreaction of 1.0 moles of zinc(II) bis(2-ethylhexanoate) with 0.5 to 1.5moles of an amidine (I).

Particular preference is given to coating material compositions whichcomprise as component (D)Zn(1,1,3,3-tetramethylguanidine)_(x)(acetate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(formate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(benzoate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(2-ethylhexanoate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(octoate)₂,Zn(1,3-diphenylguanidine)_(x)(formate)₂,Zn(1,3-diphenylguanidine)_(x)(acetate)₂,Zn(1,3-diphenylguanidine)_(x)(benzoate)₂,Zn(1,3-diphenylguanidine)_(x)(2-ethylhexanoate)₂, and/orZn(1,3-diphenylguanidine)_(x)(octoate)₂, preferablyZn(1,1,3,3-tetramethylguanidine)_(x)(2-ethylhexanoate)₂ and/orZn(1,1,3,3-tetramethylguanidine)_(x)(octoate)₂ and/orZn(1,3-diphenylguanidine)_(x)(2-ethylhexanoate)₂ and/orZn(1,3-diphenylguanidine)_(x)(octoate)₂ with x, in each case, beinggreater than or equal to 2.5, in particular x=3.0 to 4.0. Especiallypreferred are coating material compositions which comprise as component(D) Zn(1,1,3,3-tetramethylguanidine)_(x)(2-ethylhexanoate)₂ and/orZn(1,1,3,3-tetramethylguanidine)_(x)(octoate)₂ with x, in each case,being less than or equal to 1.8, in particular x=0.5 to 1.5.

The reaction of the zinc(II) biscarboxylate or biscarboxylates with theamidine or amidines (I) takes place typically in a solvent. Solventsemployed in this case are more particularly those solvents which allowsufficient solubility of the zinc(II) biscarboxylates and of thezinc-amidines and are free from isocyanate-reactive groups. Examples ofsuch solvents are the solvents (L) already recited in connection withthe polyisocyanate group-containing compound (B).

The reaction of the zinc(II) biscarboxylate or biscarboxylates with theamidine or amidines (I) may also take place in the polyhydroxylgroup-containing component (A) and/or in the low molecular mass alcoholsrecited as component (C), optionally in a mixture with furthersolvents—such as, more particularly, the solvents (L) just recited.

It is also possible to carry out the reaction of the zinc(II)biscarboxylate or biscarboxylates with the amidine or amidines (I) inthe overall mixture of the coatings component (K-I), comprising thehydroxyl group-containing compounds (A) and optionally (C), optionallythe solvent, and optionally one or more of the coatings additives (F)recited below.

The reaction of the zinc(II) biscarboxylate or biscarboxylates with theamidine or amidines (I) takes place typically at room temperature orslightly elevated temperature of up to 100° C. For this reaction,generally speaking, the zinc(II) biscarboxylate is introduced in thesolvent or in the hydroxyl group-containing compound (A) and/or (C)—asjust described—and the amidine compound, optionally in solution in oneof the stated solvents, is added slowly dropwise. After waiting for theresultant evolution of heat, the mixture is then stirred for 2 hoursmore at not less than 60° C.

In addition it is possible, particularly when the coating materialcompositions are 2-component coating material compositions, to preparethe active catalyst compound (D) in situ. For this purpose, acorresponding amount of the amidine or amidines is dissolved in thecoatings component (K-I), comprising hydroxyl-containing binder (A) andoptionally (C), and a corresponding amount of the zinc(II)biscarboxylate is dissolved in the coatings component (K-II), comprisingthe polyisocyanate group-containing compound (B). When the two coatingscomponents are mixed prior to application, the zinc-amidine complex isthen formed in situ in the coating material composition.

Monomeric Aromatic Carboxylic Acid (S)

To further improve the assembly strength of the coatings, it is furtherpreferred that the coating material composition comprises at least onemonomeric aromatic, optionally substituted carboxylic acid (S) whosecarboxyl group is in conjugation with a π-electron system. Here, thenumber of carboxyl groups may vary, the carboxylic acids preferablyhaving one carboxyl group. The monomeric aromatic, optionallysubstituted carboxylic acids preferably have a molecular weight <500g/mol, more preferably <300 g/mol. It is preferred to use monomericaromatic, optionally substituted carboxylic acids which have a pKa of 2to 5. The pKa corresponds to the pH at the half-equivalent point, thesolution medium being preferably water. Should it not be possible for anacid to specify a pKa in water, then the medium selected is preferablyDMSO or else another suitable medium in which the acid is soluble.

Suitability is possessed by monomeric aromatic monocarboxylic andpolycarboxylic acids, the corresponding alkyl- and aryl-substitutedaromatic monocarboxylic and polycarboxylic acids, and also thecorresponding hydroxyl-containing aromatic monocarboxylic andpolycarboxylic acids, such as, for example, phthalic acid andterephthalic acid, alkyl- and/or aryl-substituted phthalic acid andterephthalic acid, benzoic acid and alkyl- and/or aryl-substitutedbenzoic acid, aromatic carboxylic acids having further functional groupssuch as salicylic acid and acetylsalicylic acid, alkyl- and/oraryl-substituted salicylic acid or isomers thereof, polycyclic aromaticcarboxylic acids, such as the isomers of naphthalenecarboxylic acid, andderivatives thereof.

As monomeric aromatic carboxylic acid (S), the coating materialcomposition preferably comprises benzoic acid, tert-butylbenzoic acid,3,4-dihydroxybenzoic acid, salicylic acid and/or acetylsalicylic acid,more preferably benzoic acid.

the Combination of Components (A), (B), Optionally (C), (D), and (S),and Also Further Components of the Coating Material Compositions

Where the compositions are one-component coating material compositions,polyisocyanate group-containing compounds (B) are selected whose freeisocyanate groups are blocked with blocking agents. For example, theisocyanate groups may be blocked with substituted pyrazoles, moreparticularly with alkyl-substituted pyrazoles, such as 3-methylpyrazole,3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole,4-bromo-3,5-dimethylpyrazole, and so on. With particular preference, theisocyanate groups of component (B) are blocked with3,5-dimethylpyrazole.

In the case of the 2-component (2K) coating material compositions, whichare particularly preferred in accordance with the invention, a coatingscomponent comprising the polyhydroxyl group-containing compound (A) andalso further components, described below, is mixed shortly beforeapplication of the coating material with a further coatings component,comprising the polyisocyanate group-containing compound (B) and also,optionally, other of the components described below, mixing taking placein a manner known per se; in general, the coatings component whichcomprises the compound (A) comprises the catalyst (D) and also a part ofthe solvent.

The polyhydroxy component (A) may be present in a suitable solvent.Suitable solvents are those which allow sufficient solubility of thepolyhydroxy component. Examples of such solvents are the solvents (L)already cited in connection with the polyisocyanate group-containingcompound (B).

The weight fractions of the polyol (A) and optionally (C) and of thepolyisocyanate (B) are preferably selected such that the molarequivalents ratio of the hydroxyl groups of the polyhydroxylgroup-containing compound (A) plus optionally (C) to the isocyanategroups of component (B) is between 1:0.9 and 1:1.5, preferably between1:0.9 and 1:1.1, more preferably between 1:0.95 and 1:1.05.

It is preferred in accordance with the invention to use coating materialcompositions which comprise from 30% to 80% by weight, preferably from50% to 70% by weight, based in each case on the binder content of thecoating material composition, of at least one polyhydroxylgroup-containing compound (A), more particularly at least onepolyhydroxyl group-containing polyacrylate (A) and/or at least onepolyhydroxyl group-containing polymethacrylate (A).

Preference is likewise given in accordance with the invention to the useof coating material compositions which comprise from 5% to 50% byweight, preferably from 25% to 40% by weight, based in each case on thebinder content of the coating material composition, of thepolyisocyanate group-containing compound (B).

The coating material compositions of the invention preferably furthercomprise at least one zinc-amidine complex (D) in an amount such thatthe metal content of the zinc-amidine complex, based in each case on thebinder content of the coating material composition, is between 35 and2000 ppm, preferably between 35 and 1000 ppm, and more preferablybetween 100 and 1000 ppm.

The coating material compositions of the invention preferably furthercomprise 0% to 15.0% by weight, preferably 0.2% to 8.0% by weight, andmore preferably 0.5% to 5.0% by weight, of at least one aromaticcarboxylic acid (S), the percentages by weight being based in each caseon the binder content of the coating material composition.

By binder fraction is meant in each case the fraction of the coatingmaterial composition, prior to crosslinking, which is soluble intetrahydrofuran (THF). For this purpose, a small sample (P) is weighedout and dissolved in 50 to 100 times the amount of THF, insolubleconstituents are removed by filtration, the THF is evaporated off, andsubsequently the solids of the previously THF-dissolved constituents isascertained by drying the remaining sample at 130° C. for 60 minutes,cooling it in a desiccator, and then weighing it again. The residuecorresponds to the binder content of the sample (P).

The coating material compositions of the invention are preferablynonaqueous coating materials and may comprise solvent or may beformulated as solvent-free systems. Examples of suitable solvents arethe solvents (L) already recited for the polyhydroxyl group-containingcompound (A) and optionally (C) and for the polyisocyanategroup-containing compound (B). The solvent or solvents are used in thecoating material compositions of the invention preferably in an amountsuch that the solids content of the coating material composition is atleast 50% by weight, more preferably at least 60% by weight.

Additionally, the coating material compositions of the invention maycomprise 0% to 30% by weight, preferably 0% to 15% by weight, based ineach case on the binder content of the coating material composition, ofone or more amino resins and/or one or moretris(alkoxycarbonylamino)triazines (E).

Examples of suitable tris(alkoxycarbonylamino)triazines are given inU.S. Pat. No. 4,939,213, in U.S. Pat. No. 5,084,541, and in EP-A-0 624577.

Examples of suitable amino resins (E) are all of the amino resinstypically used in the coating industry sector, the properties of theresultant coating materials being controllable via the reactivity of theamino resin. The resins are condensation products of aldehydes,especially formaldehyde, and, for example, urea, melamine, guanamine,and benzoguanamine. The amino resins comprise alcohol groups, preferablymethylol groups, generally some of which, or preferably all of which,are etherified with alcohols. Use is made in particular of amino resinsetherified with lower alcohols. Preference is given to using aminoresins etherified with methanol and/or ethanol and/or butanol, examplesbeing the products available commercially under the names Cymel®,Resimene®, Maprenal®, and Luwipal®.

The amino resins (E) are long-established compounds and are described indetail in, for example, the American patent application US 2005/0182189A1, page 1, paragraph [0014], to page 4, paragraph [0028].

The binder mixture of the invention and/or the coating materialcomposition of the invention may further comprise at least one customaryand known coatings additive (F) in effective amounts, i.e., in amountspreferably up to 30%, more preferably up to 25%, and more particularlyup to 20%, by weight, based in each case on the binder content of thecoating material composition.

Examples of suitable coatings additives (F) are as follows:

-   -   especially UV absorbers;    -   especially light stabilizers such as HALS compounds,        benzotriazoles or oxalanilides;    -   free-radical scavengers;    -   slip additives;    -   polymerization inhibitors;    -   defoamers;    -   reactive diluents different from components (A) and (C), more        particularly reactive diluents which become reactive only        through reaction with further constituents and/or with water,        such as Incozol® or aspartic esters, for example;    -   wetting agents different from components (A) and (C), such as        siloxanes, fluorine-containing compounds, carboxylic monoesters,        phosphoric esters, polyacrylic acids and their copolymers, or        polyurethanes;    -   adhesion promoters;    -   flow control agents;    -   film-forming assistants such as cellulose derivatives;    -   fillers such as, for example, nanoparticles based on silicon        dioxide, aluminum oxide or zirconium oxide; for further details,        refer to Römpp Lexikon “Lacke and Druckfarben”, Georg Thieme        Verlag, Stuttgart, 1998, pages 250 to 252;    -   rheology control additives different from components (A) and        (C), such as the additives known from patents WO 94/22968,        EP-A-0 276 501, EP-A-0 249 201 or WO 97/12945; crosslinked        polymeric microparticles, of the kind disclosed in EP-A-0 008        127, for example; inorganic phyllosilicates such as aluminum        magnesium silicates, sodium magnesium and sodium magnesium        fluorine lithium phyllosilicates of the montmorillonite type;        silicas such as Aerosils®; or synthetic polymers having ionic        and/or associative groups, such as poly(meth)acylamide,        poly(meth)acrylic acid, poly-vinylpyrrolidone, styrene-maleic        anhydride or ethylene-maleic anhydride copolymers and their        derivatives, or hydrophobically modified ethoxylated urethanes        or polyacrylates;    -   flame retardants.

Particularly preferred are coating material compositions which comprise50% to 70% by weight, based on the binder content of the coatingmaterial composition, of at least one polyhydroxyl group-containingpolyacrylate (A) and/or at least one polyhydroxyl group-containingpolymethacrylate (A),

25% to 40% by weight, based on the binder content of the coatingmaterial composition, of the polyisocyanate group-containing compound(B),0% to 10% by weight, based on the binder content of the coating materialcomposition, of the hydroxyl-containing component (C),0.5% to 5.0% by weight, based on the binder content of the coatingmaterial composition, of at least one aromatic carboxylic acid (S),0% to 15% by weight, based on the binder content of the coating materialcomposition, of one or more amino resins and/or one or moretris(alkoxycarbonylamino)triazines (E), and0% to 20% by weight, based on the binder content of the coating materialcomposition, of at least one customary and known coatings additive (F)andcomprise at least one zinc-amidine complex (D) in an amount such thatthe metal content of the zinc-amidine complex, based in each case on thebinder content of the coating material composition, is between 100 and1000 ppm.

In a further embodiment of the invention, the binder mixture or coatingmaterial composition of the invention may further comprise otherpigments and/or fillers and may serve for producing pigmented topcoatsand/or pigmented undercoats or primer-surfacers, more particularlypigmented topcoats. The pigments and/or fillers that are used for thesepurposes are known to the skilled person. The pigments are typicallyused in an amount such that the pigment-to-binder ratio is between0.05:1 and 1.5:1, based in each case on the binder content of thecoating material composition.

Since the coatings of the invention produced from the coating materialsof the invention also adhere outstandingly to already-cured electrocoatfinishes, surfacer finishes, basecoat finishes or customary and knownclearcoat finishes, they are outstandingly suitable not only for use inautomotive OEM (production-line) finishing but also for automotiverefinish and/or for the coating of parts for installation in or onautomobiles and/or for the coating of utility vehicles.

The coating material compositions of the invention may be applied by allof the customary application methods, such as spraying, knifecoating,spreading, pouring, dipping, impregnating, trickling or rolling, forexample. In the course of such application, the substrate to be coatedmay itself be at rest, with the application equipment or system beingmoved. Alternatively, the substrate to be coated, more particularly acoil, may be moved, with the application system being at rest relativeto the substrate or being moved appropriately.

Preference is given to employing spray application methods, such as, forexample, compressed-air spraying, airless spraying, high-speed rotation,electrostatic spray application (ESTA), alone or in conjunction with hotspray application such as, for example, hot-air spraying.

The applied coating materials of the invention can be cured after acertain rest time. The rest time serves, for example, for the flow anddevolatization of the coating films or for the evaporation of volatileconstituents such as solvents. The rest time may be assisted and/orshortened by use of elevated temperatures and/or by a reducedatmospheric humidity, provided that this does not entail any damage toor change in the coating films, such as premature complete crosslinking,for instance.

There are no peculiarities of method as far as the thermal curing of thecoating materials is concerned; this curing instead takes place inaccordance with the customary and known methods such as heating in aforced-air oven or irradiation with IR lamps. Thermal curing here mayalso take place in stages. Another preferred method of curing is thatusing near infrared (NIR radiation).

Thermal curing takes place advantageously at a temperature of 20 to 200°C. for a time of 1 minute up to 10 hours, and even longer cure times maybe employed at low temperatures. For automotive refinish and for thepainting of plastics parts, and also for the finishing of utilityvehicles, it is usual to employ relatively low temperatures, which arepreferably between 20 and 80° C., more particularly between 20 and 60°C.

The coating material compositions of the invention are outstandinglysuitable for use as decorative, protective and/or effect coatings andfinishes on bodywork of means of transport (more particularly motorvehicles, such as cycles, motorcycles, buses, trucks or automobiles) orof parts thereof; of the interior and exterior of edifices; offurniture, windows, and doors; of plastics moldings, more particularlyCDs and windows; of small industrial parts, of coils, containers, andpackaging; of white goods; of films; of optical, electrical, andmechanical components; and also of hollow glassware and articles ofeveryday use.

Consequently, the coating material compositions of the invention can beapplied, for example, to an uncoated or precoated substrate, the coatingmaterials of the invention being either pigmented or unpigmented. Thecoating material compositions and finishes of the invention, moreparticularly the clearcoat finishes, are employed more particularly inthe technologically and esthetically particularly demanding field ofautomotive OEM finishing and for the coating of plastics parts forinstallation in or on automobile bodies, more particularly for top-classautomobile bodies, such as, for example, for producing roofs, tailgates,engine cowlings, fenders, bumpers, spoilers, sills, protective strips,side trim, and so on, and also for automotive refinish and for thefinishing of utility vehicles, such as, for example, of trucks,chain-driven construction vehicles, such as crane vehicles, wheelloaders, and concrete mixers, buses, rail vehicles, watercraft,aircraft, and also agricultural equipment such as tractors and combines,and parts thereof.

The plastics parts are typically composed of ASA, polycarbonates, blendsof ASA and polycarbonates, polypropylene, polymethyl methacrylates orimpact-modified polymethyl methacrylates, more particularly of blends ofASA and polycarbonates, preferably used with a polycarbonatefraction >40%, more particularly >50%.

ASA refers generally to impact-modified styrene-acrylonitrile polymerswherein graft copolymers of vinylaromatic compounds, more particularlystyrene, and of vinyl cyanides, more particularly acrylonitrile, arepresent on polyalkyl acrylate rubbers in a copolymer matrix of, inparticular, styrene and acrylonitrile.

With particular preference the coating material compositions of theinvention are used in multistage coating methods, more particularly inmethods which involve applying, to an uncoated or precoated substrate,first a pigmented basecoat film and thereafter a coat with the coatingmaterial composition of the invention. The invention accordingly alsoprovides multicoat effect and/or color coating systems comprising atleast one pigmented basecoat film and, disposed thereon, at least oneclearcoat film, characterized in that the clearcoat film has beenproduced from the coating material composition of the invention.

Not only water-thinnable basecoats but also basecoats based on organicsolvents may be used. Suitable basecoats are described in, for example,EP-A-0 692 007 and the documents cited therein at column 3, lines 50 etseq. Preferably, the applied basecoat is first dried, which means that,in an evaporation phase, at least some of the organic solvent and/or thewater is removed from the basecoat film. Drying takes place preferablyat temperatures from room temperature to 80° C. After drying has takenplace, the coating material composition of the invention is applied. Thetwo-coat finish is then preferably baked, under conditions employed inautomotive OEM finishing, at temperatures from 20 to 200° C. for a timefrom 1 minute up to 10 hours, and even longer cure times may be employedin the case of the temperatures employed for automotive refinish, whichare generally between 20 and 80° C., more particularly between 20 and60° C.

In another preferred embodiment of the invention, the coating materialcomposition of the invention is used as a transparent clearcoat for thecoating of plastics substrates, more particularly of plastics parts forinstallation in or on other articles. These plastics parts arepreferably likewise coated in a multistage coating method, whichinvolves applying, to an uncoated or precoated substrate or to asubstrate which has been pretreated for improved adhesion of thesubsequent coatings (for example, by flaming, corona treatment or plasmatreatment of the substrate), first a pigmented basecoat film andthereafter a coat with the coating material composition of theinvention.

EXAMPLES Gel Permeation Chromatography (GPC)

The gel permeation chromatography was carried out at 40° C. using ahigh-pressure liquid chromatography pump and a refractive-indexdetector. The eluent used was tetrahydrofuran, with an elution rate of 1ml/min. The calibration was carried out by means of polystyrenestandards. The number-average molecular weight Mn, the weight-averagemolecular weight Mw, and Mp were ascertained, the polydispersity indexMp being calculated from Mp=Mw/Mn.

Hydroxyl Number:

The hydroxyl number is calculated via the fraction of OH-functionalcomponents used and expressed in mg of KOH per gram of resin solids.

Solids Determination

Approximately 1 g of sample are weighed out into a tin plate lid.Following addition of around 3 ml of butyl acetate, the sample is driedin a drying cabinet at 130° C. for 60 minutes, cooled in a desiccator,and then weighed again. The residue corresponds to the solids fraction.

Binder Content Determination

The binder fraction means in each case that fraction of the coatingmaterial composition that is soluble in tetrahydrofuran (THF), prior tocrosslinking. For its determination, a small sample (P) is weighed out,dissolved in 50 to 100 times the amount of THF, insoluble constituentsare removed by filtration, the THF is evaporated off, and then thesolids of the constituents previously dissolved in THF is ascertained bydrying at 130° C. for 60 minutes, cooling in a desiccator, and thenrepeat weighing. The residue corresponds to the binder content of thesample (P).

Freedom from Tack by the Zapon Tack Test (ZTT):

An aluminum strip with a thickness of 0.5 mm, a width of 2.5 cm, and alength of 11 cm is bent at an angle of 110° to give a surface measuring2.5×2.5 cm. The long side of the metal plate is bent, after a further2.5 cm, by about 15°, so that the plate is just held in balance by aweight (5 g) placed in the center of the square area. For themeasurement of the ZTT tack-free state, the bent plate is placed on thecoating film and weighed down with a 100 g weight for 30 seconds.Following removal of the weight, the coating is considered tack-free ifthe metal angle falls over within 5 s. The test is repeated at intervalsof 15 minutes. Before the test is deployed, the tackiness of the coatingfilm is assessed qualitatively by touch. In the case of tests atelevated temperature, the test panels are stored at room temperature for10 minutes for cooling before the test is commenced.

Print Test:

The coating film is drawn down using a 100 micrometer applicator onto aglass plate. After drying at 60° C. for 15 minutes, the glass plate,within a period of 10 minutes following removal from the oven, is placedon a commercial laboratory balance. Using thumb pressure, the film isthen loaded with a weight of 2 kg for 20 seconds. This test is repeatedevery 10 minutes. In the case of a coating film which is obviously stillsoft or tacky, the coating film is first left until it has reached asufficient freedom from tack, and a sufficient hardness. The tests areevaluated after a storage time of 24 hours. For the evaluation, thesurface of the coating is washed off with aqueous surfactant solution(commercial washing-up detergent) and a soft cloth, in order to removegrease marks. Measurement is always against a standard. The coating isconsidered satisfactory if there is no visible thumb imprint on thecoating film. This test is a measure of the assembly strength ofrefinishes—the earlier that the coating film has attained its assemblystrength after forced drying, the earlier that assembly operations (ordisassembly operations to remove adhesive masking) may be commenced onthe refinished bodywork.

Drying Recorder:

The coating is drawn down using a 100 micrometer four-way bar applicatoronto glass plates with dimensions of 280 mm×25 mm. With the aid of theByk Dry-time Recorder, needles are drawn over the film at a definedspeed, at room temperature (20-23° C.) and a relative humidity of 40% to60%. Assessments are made of 3 different phases and also of the totallength (i.e., sum of phase 1+phase 2+phase 3) of the track.

Phase 1: the needle track closes up again

Phase 2: the needle track results in a deep furrow in the coating film

Phase 3: the needle causes only superficial damage to the film

The assessment is always undertaken against a standard.

Potlife:

For this, the viscosity of a paint sample is measured at roomtemperature in the DIN4 flow cup. Beforehand, the sample is adjusted toa flow viscosity of 19-20 seconds in the DIN4 cup. Thereafter, theincrease in viscosity is determined at suitable time intervals. As soonas the sample has doubled its initial viscosity, the potlife limit isreached.

Pendulum Hardness:

The hardness of the paint films is determined by means of pendulumdamping according to Koenig in accordance with DIN 53157. The pendulumstrikes are reported.

WOM Test (Yellowing)

A commercial 2K-PU auto repair filler and, on top of that, a glazingwater basecoat material of the 90 series from BASF Coatings GmbH, shade;silver, on 2 test panels is coated with the clearcoat material frominventive example 1 and comparative example C2 under test, with a filmthickness of 30-40 μm. One of these test panels is weathered inaccordance with the standard SAE J2527-04 (WOM test). After intervals oftime fixed beforehand, the panel is removed from the weatheringapparatus, subjected to measurement with the multiple angle colorimeterBYK-mac from BYK-Gardner GmbH, D-82538 Geretsried, with calculation inaccordance with DIN 6174 with absolute values, and again exposed in theweathering apparatus. The yellowing is assessed against a co-testedstandard coating based on tin-containing catalysts.

Millbase:

86.4 g of a styrene-containing polyacrylate (62% inSolventnaphtha®/ethoxyethyl propionate/methyl isobutyl ketone(20/46/34)) having a molecular weight of 1600-2200 (Mn) and 4000-5000(Mw), a measured acid number of 12-16 mg KOH/g, a calculated OH number(OHN) of about 130 mg KOH/g (resin solids), and a viscosity of the 60%strength solution in butyl acetate of 200-400 mPa·s, measured using arotary viscometer (Brookfield CAP 2000, spindle 3, 1000 rpm), arestirred together with 6.4 g of methyl isobutyl ketone, 2.2 g of acommercial light stabilizer mixture composed of UV and HALS lightstabilizers and also with 0.15 g of a commercial flow control agentbased on a polyacrylate, to form a homogeneous mixture. Added to thismixture, where indicated, is the corresponding catalyst, which is mixedin with stirring. When benzoic acid is used, it is dissolved as a solidin the millbase mixture, with stirring. For adjustment of viscosity, afurther 1.0 parts of methyl isobutyl ketone and 2.80 parts of butylacetate are added.

Curing Agent Solution:

In a mixture of 5.17 parts of xylene, 7.48 parts of butyl acetate, 1.506parts of ethyl ethoxypropionate, 7.03 parts of methyl isobutyl ketone,and 0.3 part of a commercial flow control agent based on a polyacrylate(55% in Solventnaphtha®), 28.1 g of trimerized hexamethylenediisocyanate (HDI) containing isocyanurate groups and having anisocyanate content of 22.0%, based on the solvent-free trimerizedhexamethylene diisocyanate, are dissolved.

Catalysts: Catalyst K1

60.27 g of zinc(II) bis(2-ethylhexanoate) (0.171 mol) are dissolved in20.0 g of butyl acetate. 19.73 g of 1,1,3,3-tetramethylguanidine (0.171mol) are added slowly dropwise. After the exothermic reaction hassubsided, stirring is continued at RT° C. for 20 minutes more.

Catalyst K2

48.34 g of zinc(II) bis(2-ethylhexanoate) (0.137 mol) are dissolved in20 g of butyl acetate. 31.656 g of 1,1,3,3-tetramethylguanidine (0.275mol) are added slowly dropwise. After the exothermic reaction hassubsided, stirring is continued at RT° C. for 20 minutes more.

Experimental Procedure

Additional components such as benzoic acid and catalyst solutions aredissolved in the millbase. Following gentle stirring, clear solutionsare obtained. For the implementation of the experiments, the millbase isintroduced and the curing agent is added. The solution is homogenized bystirring. For the viscosity measurements, adjustment to the specifiedviscosity is made by addition of solvent. For the glass drawdowns, theviscosity adjustment is not made. For the drying test, the coating filmis drawn down using a 100 μm four-way bar applicator onto glass platesto produce a film thickness of 30-35 μm. For the testing of the pendulumhardness, the film is poured onto glass plates, and before the Koenigfilm hardness is ascertained, the thickness of the applied film at thescore mark (DIN 50933) is measured. For the tests using a dryingrecorder, the samples are likewise drawn down using a 100 μm four-waybar applicator onto suitable glass strips with length of approximately300 mm and a width of approximately 25 mm; the film thicknesses achievedthereby are 30-35 μm.

Inventive Examples 1 and 2 and Comparative Examples C1 and C2

First of all, the coating materials of inventive examples 1 and 2 wereprepared with the same amount of the same zinc-amidine complex but oncewith benzoic acid (inventive example 1) and once without benzoic acid(inventive example 2). In comparative example C1, a coating materialcomposition based on tin-containing catalysts was prepared first of all.In addition, the coating material of comparative example C2 was preparedin analogy to WO06/022899 with theZn(1,1,3,3-tetramethylguanidine)₂(2-ethylhexanoate)₂ complex and withoutaromatic carboxylic acid. The composition of these coating materials ofinventive examples 1 and 2 and of comparative examples C1 and C2, andalso the test results on the resultant coatings, are set out in table 1.

TABLE 1 Composition of the coating materials of inventive examples 1 to3 and of comparative example C1 in parts by weight, and the test resultsof the resultant coatings I1 I2 C1 C2 Millbase 98.97 98.97 98.97 98.97DIBUTYLTIN DILAURATE 0.06 Benzoic acid 2.41 1.5 Catalyst K2 0.25Catalyst K1 0.2 0.2 Curing agent solution 49.58 49.58 49.58 49.58 Metalcontent¹⁾ [ppm] 275 275 140 275 Potlife DIN 4 [s]²⁾ direct 19 21 19 21after 1 h 24 25 23 26 after 2 h 31 32 36 30 after 3 h 51 37 78 39 ZAPONtack 30 min 60° C./10 min RT [min]³⁾ 15 265 0 280 Pendulum damping 23°C. RT after 1 d⁴⁾ 94 72 39 74 23° C. RT after 7 d⁴⁾ 134 138 69 13330′60° C. after 1 d⁵⁾ 98 95 64 112 30′60° C. after 7 d⁵⁾ 145 149 83 148Drying Recorder⁶⁾ Total length [cm] 17.3 26.6 17.2 25.2 Phase 1 [cm] 5.57 4.4 6.9 Phase 2 [cm] 7 12.1 6.5 11.2 Phase 3 [cm] 4.8 7.1 6.3 7.1Print test - 15 min 60° C./10 min 60 340 80 340 RT⁷⁾ [min] Key to table1 ¹⁾reported is the amount of catalyst K1 or K2 in ppm of metal content,based on the binder fraction of the coating material composition²⁾reported is the viscosity of the coating material composition asmeasured at room temperature in the DIN4 flow cup, directly afterpreparation and also after 1, 2 and 3 hours after its preparation³⁾measurement of the freedom from tack by the Zapon tack test aftercuring of the coating at 60° C. for 30 minutes, and beginning of thetest after storage of the panels at room temperature for 10 minutes⁴⁾measurement of the pendulum hardness after storage of the coating for1 or 7 days at room temperature ⁵⁾measurement of the pendulum hardnessafter curing of the coating for 30 min at 60° C. and subsequent storageof the coating for 1 or 7 days at room temperature ⁶⁾reported is thetotal length of the scratch track in cm, and also the length of thescratch track in cm after each of phases 1, 2, and 3 ⁷⁾reported is thetime in minutes after which the imprint in the print test is no longervisible after drying at 60° C. for 15 minutes and after subsequentstorage of the panels at room temperature for 10 minutes

Discussion of the Test Results

The comparison of the results of the pendulum damping and of the dryingrecorder for inventive examples 1 and 2 with the results of comparativeexample C1 shows that the through-curing of the coating materials of theinvention is comparable with the through-curing of the conventionalcoating materials based on tin-containing catalysts. However, thecoating material compositions of the invention of inventive example 1and 2 have a significantly improved, i.e. longer, potlife than theconventional coating material compositions based on tin-containingcatalysts of comparative example C1.

As shown by the comparison of the print test results of inventiveexamples 1 and 2 with comparative example C1, the coating materials ofthe invention are at the same time notable for relatively rapid curing,even under the conditions of refinish, and hence for good assemblystrength after just a relatively short time, whereas, typically, aprolonged potlife with a poorer, i.e., slower, curing and therefore goodassembly strength is obtained only after a significantly longer time.The assembly strength can surprisingly be achieved after a significantlyshorter time as a result of the addition of benzoic acid, without anyserious adverse effect on the potlife as a result as shown by thecomparison of inventive examples 1 and 2.

As shown by the results of the print test for comparative example C2,the coating materials based on theZn(1,1,3,3-tetramethylguanidine)₂(2-ethylhexanoate)₂ complex, butwithout the addition of the benzoic acid, exhibit significantly slowercuring under the conditions of refinish, and hence a poorer assemblystrength, than the coating materials of the invention with addition ofbenzoic acid as in inventive example 1.

The coating materials of the invention and the corresponding coatingswith the catalyst C1, as compared with the coating material and thecorresponding coating from comparative example C2 with the catalyst C2in accordance with WO06/022899, with a comparable amount of metal in theformulation, exhibit significantly lower yellowing. The correspondingresults of colorimetry (following production of the coatings, they werefirst stored at room temperature for 24 hours prior to colorimetry)using the multiple-angle colorimeter BYK-mac from BYK-Gardner GmbH,D-82538 Geretsried, and calculation according to DIN 6174, with absolutevalues set out as CieLab values, are set out in table 2. The “delta”values in table 2 are in each case equal to the difference in colorvalue for the coating of the comparative example C2 minus the colorvalue of the coating of inventive example 1.

TABLE 2 Results of colorimetry, set out as CieLab values, for thecoating of comparative example C2 and the coating of inventive example 1L* a* b* C2 −15  149.98 −0.89 0.18 15 136.15 −0.59 0.17 25 107.53 −0.62−0.92 45 62.93 −0.61 −1.19 75 38.93 −0.46 −0.54 110  32.82 −0.62 −0.35I1 −15  145.6 −0.92 0.26 15 135.45 −0.63 0.23 25 107.37 −0.63 −0.88 4563.4 −0.62 −1.19 75 39.49 −0.49 −0.55 110  33.26 −0.62 −0.37 Delta¹⁾dL¹⁾ da¹⁾ db¹⁾ −15  4.38 0.03 −0.08 15 0.70 0.04 −0.06 25 0.16 0.01−0.04 45 −0.47 0.01 0.00 75 −0.56 0.03 0.01 110  −0.44 0.00 0.02 ¹⁾=respective color value for comparative example C2 minus color value ofinventive example 1

The differences in the lightness can be explained through differentdevelopment of effect, as a result of slight differences in paintapplication by manual painting. The coating of inventive example 1,particularly at the viewing angles of −15°/115°/125° in the db value(=blue-yellow deviation), shows that the coating of inventive example 1is less yellowish than the coating of comparative example C2.

1. The coating material composition comprising at least one polyhydroxylgroup-containing compound (A), at least one polyisocyanategroup-containing compound (B) having free and/or blocked isocyanategroups, and at least one catalyst (D) based on a zinc-amidine complexwhich is comprises the reaction product of 1.0 moles of one or morezinc(II) biscarboxylates with less than 2.0 moles of an amidine of theformula (I) or with less than 2.0 moles of a mixture of two or moreamidines of the formula (I)

where R₅=hydrogen and R₁, R₂, R₃, and R₄ are each identical or differentradicals, R₁ and R₃ being hydrogen or an alkyl radical or an arylradical, and R₂ and R₄ being an alkyl radical or an aryl radical.
 2. Thecoating material composition of claim 1, wherein the radicals R₂ and R₄are identical or different radicals selected from the group consistingof acyclic alkyl radicals, straight-chain alkyl radicals, branched alkylradicals, aryl radicals, and mixtures of two or more of the foregoing,and wherein the radicals R₁ and R₃ are identical or different membersselected from the group consisting of hydrogen, acyclic alkyl radicals,straight-chain alkyl radicals, branched alkyl radicals, aryl radicals,and mixtures of two or more of the foregoing.
 3. The coating materialcomposition of claim 1, wherein the zinc-amidine complex is selectedfrom the group consisting of the reaction product of 1.0 moles of one ormore zinc(II) biscarboxylates with 0.1 to 1.8 moles of an amidine of theformula (I), the reaction product of 1.0 moles of one or more zinc(II)biscarboxylates with 0.1 to 1.8 moles of a mixture of two or moreamidines of the formula (I).
 4. The coating material composition ofclaim 1, wherein the carboxylate radical of the zinc-amidine complex (D)is selected from the group consisting of carboxylate radicals ofaliphatic linear and/or branched, optionally substituted monocarboxylicacids having 1 to 12 C atoms in the alkyl radical, aromatic, optionallysubstituted monocarboxylic acids having 6 to 12 C atoms in the arylradical and mixtures of two or more of the foregoing.
 5. The coatingmaterial composition of claim 1, wherein the coating materialcomposition comprises as component (D) a member selected from the groupconsisting of Zn(1,1,3,3-tetramethylguanidine)_(x)(acetate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(formate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(benzoate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(2-ethylhexanoate)₂,Zn(1,1,3,3-tetramethylguanidine)_(x)(octoate)₂,Zn(1,3-diphenylguanidine)_(x)(formate)₂,Zn(1,3-diphenylguanidine)_(x)(acetate)₂,Zn(1,3-diphenylguanidine)_(x)(benzoate)₂,Zn(1,3-diphenylguanidine)_(x)(2-ethylhexanoate)₂,Zn(1,3-diphenylguanidine)_(x)(octoate)₂, and mixtures of two or more ofthe foregoing with x, in each case, being less than or equal to 1.8. 6.The coating material composition of claim 1, wherein the coatingmaterial composition further comprises at least one monomeric aromatic,optionally substituted carboxylic acid (S) whose carboxyl group is inconjugation with a π-electron system.
 7. The coating materialcomposition of claim 6, wherein the coating material compositioncomprises as carboxylic acid (S) a member selected from the groupconsisting of benzoic acid, tert-butylbenzoic acid, 3,4-dihydroxybenzoicacid, salicylic acid, acetylsalicylic acid, and mixtures of two or moreof the foregoing.
 8. The coating material composition of claim 1,wherein the coating material composition comprises at least onezinc-amidine complex (D) in an amount such that the metal content of thezinc-amidine complex, based in each case on the binder fraction of thecoating material composition, is between 35 and 2000 ppm, and/or thecoating material composition comprises 0% to 15.0% by weight, of atleast one aromatic carboxylic acid (S), the percentages by weight inturn being based in each case on the binder fraction of the coatingmaterial composition.
 9. The coating material composition of claim 1,wherein the coating material composition comprises as component (B) atleast one compound having free isocyanate groups and/or in that itcomprises as component (B) a member selected from the group consistingof 1,6-hexamethylene diisocyanate, isophorone diisocyanate,4,4′-methylenedicyclohexyl diisocyanate, the biuret dimers of theaforementioned diisocyanates, the isocyanurate trimers of theaforementioned diisocyanates, the asymmetric trimers of theaforementioned diisocyanates, and mixtures of two or more of theforegoing.
 10. The coating material composition of claim 1, wherein thepolyhydroxyl group-containing compound (A) is selected from the groupconsisting of polyacrylate polyols, polymethacrylate polyols, polyesterpolyols, polyurethane polyols, polysiloxane polyols, and mixtures of twoor more of the foregoing.
 11. The coating material composition of claim1, wherein the coating material composition further comprises one ormore hydroxyl-containing compounds (C) different from component (A),and/or in that the molar equivalents ratio of the hydroxyl groups in thehydroxyl-containing compound (A) plus optionally (C) to the isocyanategroups of component (B) is between 1:0.9 and 1:1.5.
 12. The coatingmaterial composition of claim 1, comprising a nonaqueous coatingmaterial composition and/or further comprising pigments.
 13. Amultistage coating method comprising applying to an optionally precoatedsubstrate a pigmented basecoat film and thereafter a film of the coatingmaterial composition of claim 1 that may be pigmented or unpigmented.14. The multistage coating method of claim 13, wherein application ofthe pigmented basecoat film is followed first by drying of the appliedbasecoat material at temperatures from room temperature to 80° C., andthe application of the coating material composition of claim 1 isfollowed by curing at temperatures between 20 and 80° C.
 15. The methodof claim 13 wherein the coating material compositions of claim 1 is aclearcoat material or a pigmented coating material for automotiverefinish and the optionally precoated substrate is selected from thegroup consisting of parts for installation in or on automobiles,plastics substrates, of utility vehicles, and mixtures of two or more ofthe foregoing.
 16. The method of claim 13 wherein the coating materialcomposition of claim 1 is applied to a previously coated substrate andthe coating material composition is an automotive refinish coatingmaterial composition.
 17. A catalyst system for catalysis of a urethanereaction in coating material compositions comprising at least onepolyisocyanate group-containing component and at least one polyhydroxylgroup-containing component, comprising at least one zinc-amidine complex(D) which is the reaction product of 1.0 moles of one or more zinc(II)biscarboxylates with less than 2.0 moles of one or more amidines of theformula (I), and optionally at least one monomeric aromatic carboxylicacid (S) whose carboxyl group is in conjugation with a π-electronsystem.